That's been implemented as of last month, however I am waiting to upload a new demo until after I have some more story based content to show
Viewing post in The Transylvania Adventure of Simon Quest (Demo) comments
Yes- while the slide is on by default in the demo, it's not part of the normal game. It's intended for a game mode that gives you the "Ninja-Esque Bandanna", which gives you sliding, backflips, etc. There are various gameplay modifiers that change how Simon attacks, moves, jumps, etc and provide a more tongue and cheek experience.